340 EVENINGS AT THE MICROSCOPE. 



the unassisted eye. But by the aid of the lens you see 

 that each line is a long and slender thread, which creeps 

 along the glass, and at length starts out from it free for 

 a short distance, and is then terminated by a long club- 

 shaped body, which carries at its extremity four horizon- 

 tally divergent organs, like the arms of a turnstile. 

 Tracing down the threads to their lower extremities, you 

 see that they are branches of one thread, which creeps 

 irregularly over a filamentous sea-weed growing from a 

 stone in the jar. The sea-weed had been in the vessel 

 for several weeks, and the water having been undisturbed, 

 the knobbed thread, which was originally confined to 

 the plant, continued to grow, and, coming in contact with 

 the glass, spread upon it. Many other threads have 

 extended from the creeping root, some of which stand 

 up freely in the water, with their knobbed extremities 

 floating in the wave. 



This is one of the Polype tribe, named Stauridia pro- 

 ducta, and as its form and structure are interesting, we 

 will devote a few moments to its examination. We can 

 easily sever one or two of the freely floating threads, 

 and transfer the amputated portions to one of the live 

 boxes of the microscope. The motions and appearance of 

 the club with its organs will be, for a while, little 

 affected by the violence. 



The long cylindrical thread is inclosed in a transparent 

 horny tube, which, however, so closely invests it, that it 

 is with difficulty distinguished. The club-shaped head, or 

 individual polype, is an enlargement of the thread, which 

 protrudes from the investing tube. It is swollen in the 

 middle and rounded at the end ; and many of the heads, 

 which are more ventricose than the rest, contain a bubble 

 of air in the centre. This air is doubtless taken-in at the 

 mouth, which is situated at the extremity ; for, though 

 you can discern no perforation, yet there is an aperture 

 capable of being opened widely at the pleasure of the 



